Tobacco cigarette smoking remains the leading global cause of preventable disease and death killing near- ly 6 million people each year, with most of these deaths occurring in low and middle income countries (LMICs). The potential of mHealth, especially mobile phone-based strategies, to transform health care, change health behaviors, and improve health has particular significance for LMICs where access to health providers and care is limited. Preconception and pregnancy smoking are high in the Central and Eastern Europe (CEE) with life- time negative health effects for the women and their children. There are higher odds of female smoking persis- tence during pregnancy, as well as relapse once pregnant women quit, when the male partner also smokes. It is critically important to address the smoking behavior of couples during their reproductive life. Building on our work in Romania and other CEE countries, the objectives of this application are to deter- mine in a randomized controlled trial (RCT) whether a mHealth couples intervention shows promise in increas- ing smoking cessation among pregnant couples who smoke and to build mHealth research capacity in Roma- nia. We will build on Self-Determination Theory (SDT) and Motivational Interviewing (MI), a counselling style that is successful in assisting people to quit smoking. The intervention will be novel in its use of the unique functionality of smartphones, its emphasis on the dyadic efficacy for smoking cessation, and the focus on pregnant couples. Our aims are to (1) Test the implementation feasibility, acceptability, and initial efficacy of a culturally-adapted mHealth smoking cessation intervention among couples during pregnancy and postpartum in Romania. We will recruit 60 pregnant smokers and their partners; (2) Develop mHealth research capacity by enhancing individual and institutional research capabilities in Romania and expanding the existing international research network. The study will generate a base of preliminary evidence that can be used to launch a large scale R01 pro- ject to test the effectiveness of the proposed smoking prevention intervention. With respect to expected out- comes, the proposed application is anticipated to advance understanding of the effectiveness of a proactive mHealth couple intervention enhanced by addressing couples' dyadic efficacy for smoking cessation in reduc- ing pregnancy smoking and postnatal relapse. Such results are anticipated to have a system wide sustainable positive impact on the prevention of prenatal and postnatal family smoking as the intervention has a high po- tential to be adopted in the universal health system in Romania, with applications to the US and other popula- tions. This research is also expected to have a significant impact on the methodology and design of mHealth interventions during the reproductive years. The development of the international research network and the individual and institutional mHealth research capacity building is expected to positively impact mHealth re- search in CEE and the neighboring region applied to tobacco control and other locally-relevant topics.